Vehicle control device and vehicle control method

ABSTRACT

A cruise control device and an obstacle detection device are provided which achieve a safe and appropriate tracking control by avoiding a sudden recognition of a short following distance when a preceding vehicle is found in an uphill or downhill gradient, in a curve, or at an intersection, or by reducing the damage of a crash when the crash cannot be avoided. An obstacle determination process section is provided which receives information from a sensor which detects an obstacle, receives terrain information of the position of the host vehicle from a navigation device, and determines the presence of the obstacle when a predetermined condition is satisfied after the sensor detects the obstacle. The predetermined condition to determine the presence of the obstacle is changed based on the terrain information of the position of the host vehicle received from the navigation device.

FIELD OF THE INVENTION

The present invention relates to a vehicle control device and a vehiclecontrol method. In particular, the present invention is preferablyapplied to vehicles provided with means for detecting obstacles, avehicle in front (a preceding vehicle), and the like.

BACKGROUND OF THE INVENTION

An adaptive cruise control device (hereinafter, referred to as ACCdevice) realizes a function in which a driver can specify a target speedand a target distance to the preceding vehicle (a target followingdistance) through an input and output display unit, and a function of,when there is no preceding vehicle, controlling the actual speed so asto match the target speed and of, when there is a preceding vehicle,following the preceding vehicle while maintaining the target followingdistance. The ACC device is conventionally intended to be used inexpress highways, but is now increasingly used in general roads whichhave more curves and undulations. However, in a case where a precedingvehicle or a stationary object exists beyond an uphill gradient butcannot be seen, when the host vehicle reaches at the top of thegradient, the preceding vehicle or the stationary object suddenly comesinto sight. Accordingly, it is difficult for the ACC device to rapidlyreduce the speed, giving a feeling of danger in some cases. The ACCdevice usually requires several seconds to recognize a precedingvehicle. The presence of the preceding vehicle is continuously checkedfor the several seconds to judge whether the preceding vehicle isfinally determined. Control commands are issued to an alarming deviceand actuators (such as an accelerator, a transmission, and a brake),based on the determination result. Therefore, through a usual precedingvehicle determination process, timing to start deceleration is delayedbecause the presence of the preceding vehicle needs to be checked forseveral seconds. Further, when the host vehicle is driven from adownhill gradient to an uphill gradient and finds a preceding vehiclelocated in the uphill gradient, timing to start deceleration is alsodelayed because the sensor uses a required determination time to checkthe presence of the preceding vehicle although the preceding vehicle hasbeen visually found.

In short, with current ACC devices and crash reduction braking devices,braking tends to be used later than when the driver brakes the hostvehicle after visual recognition. Since the preceding vehicle has comeinto sight of the driver, it is necessary for the driver to rapidlystart deceleration.

Since a pre-crash speed is a key in cruise control systems, especially,in crash reduction braking devices, reduction in detection time isimportant. FIGS. 1A and 1B show a running distance and a deceleratedspeed, respectively, calculated by the following formulae 1 and 2:Running distance=host vehicle speed×running time  Formula 1Decelerated speed=deceleration×running time  Formula 2

For example, when the host vehicle is driven at a speed of 65 kilometersper hour, the host vehicle runs 36.1 meters for two seconds as shown inFIG. 1A. Further, for two seconds, the speed of the host vehicle can bereduced by 15.7 kilometers per hour at a deceleration of 0.8 g. Since itis known that a death rate is reduced when the speed at crash is reducedto 50 kilometers per hour or below, the pre-crash speed needs to bereduced as low as possible. In other words, when the time required forcrash judgment is reduced in seconds, a great effect is obtained.

Further, there is a known technique of using a navigation device tojudge structures such as an ETC gate and a railroad crossing at an earlystage and to find a preceding vehicle at an early stage according to thedegree of road congestion (for example, see JP-A-2003-141698).

However, it is difficult to find a preceding vehicle in a gradient or ina curve at an early stage, and there is no invention of achieving promptrecognition of a preceding vehicle in a gradient or in a curve.

On the other hand, maps have been more precise in navigation devices,and it is known that terrain information is included in the navigationdevices.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a cruise control deviceand an obstacle detection device for achieving a safe and appropriatetracking control by reducing a sudden recognition of a short followingdistance when a preceding vehicle is found in an uphill or downhillgradient, in a curve, or at an intersection, or by reducing the damageof a crash when the crash cannot be avoided.

Therefore, obstacle detection information from a sensor that detectsobstacles and terrain information of the position of the host vehiclefrom a map database are input; and if a process of determining thepresence of an obstacle is performed when a given condition is satisfiedafter the sensor detects the obstacle, a condition to determine thepresence of the obstacle is changed based on the terrain information ofthe position of the host vehicle.

Accordingly, it is possible to find early that a preceding vehicleexists at a position in a downhill gradient beyond an uphill gradient, apreceding vehicle exists at a position in an uphill gradient beyond adownhill gradient, and a preceding vehicle exists at a position beyond acurve or an intersection, so that a sudden recognition of a shortfollowing distance is reduced or the crash reduction braking device canbe activated early, thereby performing more appropriate cruise control.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows a running distance with respect to time and FIG. 1B showsa decelerated speed with respect to time, according to an embodiment ofthe present invention.

FIG. 2 is a block diagram of this embodiment.

FIG. 3 is another block diagram (2) of this embodiment.

FIGS. 4A to 4D illustrate a case where the host vehicle passes throughthe vicinity of the top of a gradient and suddenly finds a precedingvehicle.

FIG. 5 illustrates a case where the host vehicle passes through thevicinity of the bottom of a gradient and suddenly finds a precedingvehicle.

FIG. 6 illustrates a case where the host vehicle passes through thevicinity of a curve and suddenly finds a preceding vehicle.

FIG. 7 illustrates a case where the host vehicle suddenly finds apreceding vehicle beyond an intersection.

FIG. 8 is a process flow from sensor detection to vehicle control.

FIGS. 9A and 9B are timing charts of preceding vehicle detection.

FIG. 10 shows data exchange between an obstacle determination processand a navigation device.

FIG. 11 shows the obstacle determination process.

FIG. 12 shows a terrain condition search process.

FIGS. 13A and 13B illustrate how to obtain gradient differences andtraveling-direction differences.

FIG. 14 shows a process performed in the navigation device.

FIGS. 15A to 15C illustrate an example of detection (in a gradient)using a laser radar.

FIGS. 16A to 16E illustrate an example of detection (in a curve) usingthe laser radar.

FIGS. 17A to 17B are example timing charts of detection using the laserradar.

FIG. 18 shows an example of a recognition process using the laser radar.

FIG. 19 shows the principle of a stereo camera.

FIG. 20 shows an example of a recognition process using the stereocamera.

FIG. 21 shows an example of a recognition process using a millimeterwave radar.

FIG. 22 shows example determination conditions used for respectivesensors.

FIG. 23 shows another data exchange (2) between the obstacledetermination process and the navigation device.

FIG. 24 shows another terrain condition search process (2).

FIG. 25 shows another process (2) performed in the navigation device.

FIG. 26 shows a method of generating a map having terrain conditions.

FIG. 27 shows still another data exchange (3) between the obstacledetermination process and the navigation device.

FIG. 28 shows still another obstacle determination process (3).

FIG. 29 shows a terrain information table acquisition process.

FIG. 30 shows still another terrain condition search process (3).

FIG. 31 shows still another process (3) performed in the navigationdevice.

FIG. 32 shows variations of alarming and braking.

FIG. 33 is another process flow (2) from sensor detection to vehiclecontrol.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments to be described below relate to an adaptive cruise controldevice, a crash reduction braking device, and a sensor used therein, andshows reduction in judging time required to determine a precedingvehicle by using a navigation device, when the preceding vehicle isdetected in a gradient, in a curve, or at an intersection.

As shown in a block diagram of FIG. 2, a cruise control device accordingto an embodiment of the present invention includes a sensor 201 thatdetects a following distance and a relative speed, a navigation device202 that obtains terrain information of the position of the host vehicleand terrain information of the position of a preceding vehicle which isa following distance ahead of the host vehicle, on a map, aninter-vehicle control device 203 that performs constant speed control,following distance control, and pre-crash deceleration control, a brakecontrol device 204, an engine control device 205, and a communicationcable 206 that is used to exchange necessary data. The engine controldevice 205 performs transmission control. The sensor 201 includes anobstacle detection section 207 that performs an input process and arecognition process in the sensor 201.

The inter-vehicle control device 203 is realized mainly by softwareprocessing and includes an obstacle determination section 208 and aninter-vehicle control section 209. The obstacle determination section208 may be included in the inter-vehicle control device 203 as in thisexample, or may be included in the sensor 201. A function of theinter-vehicle control device 203 may be included in the sensor 201, thenavigation device 202, or another control unit.

As shown in a block diagram of FIG. 3, an obstacle recognition deviceaccording to a first embodiment of the present invention includes thesensor 201 that detects a following distance and a relative speed, thenavigation device 202 that serves as a map database to obtain terraininformation of the position of the host vehicle and terrain informationof the position of a preceding vehicle which is a following distanceahead of the host vehicle, on a map, and the communication cable 206that is used to exchange necessary data. The sensor 201 includes theobstacle detection section 207 that performs an input process and arecognition process in the sensor 201, and the obstacle determinationsection 208 that determines the presence of an obstacle and sends aresult to the inter-vehicle control device 203.

FIG. 2 shows the cruise control device according to the embodiment ofthe present invention, which includes the sensor 201 that detects thefollowing distance and relative speed to a preceding vehicle, thenavigation device 202 that obtains terrain information of the positionsof the preceding vehicle and the host vehicle, the inter-vehicle controldevice 203 that controls the following distance, the brake controldevice 204 that controls a brake, the engine control device 205 thatcontrols an engine, and the communication cable 206 that connects theabove-mentioned devices. The engine control device 205 also performstransmission control. A controller area network (CAN) is used forcommunications performed between the above-mentioned devices via thecommunication cable 206. Information necessary for cruise control, suchas the speed of the host vehicle, can be obtained constantly through theCAN. The sensor 201 includes the obstacle detection section 207 thatperforms an input process in the sensor 201. The sensor 201 sends anobstacle recognition and determination result to the inter-vehiclecontrol device 203 via the CAN.

Instead of the CAN, a dedicated communication cable may be used toexchange data between the navigation device 202 and the sensor 201.Alternatively, data may be exchanged by radio. In either case, inputsections that receive information from the sensor 201 and from thenavigation device 202 need to be provided for the inter-vehicle controldevice 203. In a case of using the CAN or the dedicated communicationcable, the input sections correspond to connectors connecting the cable.In a case of using radio, the input sections correspond to antennas. Aninput section that receives information from the navigation device 202is called a terrain information input section, and an input section thatreceives information from the sensor 201 is called a sensor informationinput section.

Control processing of the obstacle determination section 208 of thisembodiment is realized by software processing, and the software isstored in the sensor 201 or the navigation device 202.

Hereinafter, a conventional detection method and a conventionalpreceding vehicle determination process will be described.

FIGS. 4A to 4D illustrate a case where the host vehicle passes throughthe vicinity of the top of a gradient and suddenly finds a precedingvehicle. In FIGS. 4A to 4B, a hatched vehicle corresponds to the hostvehicle and an outlined vehicle corresponds to another vehicle or thepreceding vehicle (the same applies to the drawings to be referred tobelow). In FIG. 4A, the preceding vehicle has not been found. In FIG.4B, the driver of the host vehicle visually finds the preceding vehicle.In FIG. 4C, the sensor of the host vehicle starts to detect thepreceding vehicle. In FIG. 4D, the sensor of the host vehicle determinesthe presence of the preceding vehicle.

Soon after the driver of the host vehicle visually finds the precedingvehicle, the sensor of the host vehicle starts to detect the precedingvehicle. The inter-vehicle control device makes a judgment aboutdetermination of the presence of the preceding vehicle after a givenrequired determination time elapses, in order to avoid a falserecognition. However, in the case shown in FIGS. 4A to 4D, since thepresence of the preceding vehicle is determined when the host vehiclecomes rather close to the preceding vehicle, the driver needs to presson the brake. The driver, who has already found the preceding vehicle,expects that the inter-vehicle control device is activated to perform anautomatic deceleration operation, but the deceleration operation is notperformed, disappointing the driver for a moment.

FIGS. 15A to 15C illustrate an example of detection in a gradient usinga laser radar.

When a preceding vehicle suddenly appears in a lower part of thegradient as shown in FIG. 15B, three points at the center, right, andleft parts on the rear of the preceding vehicle are detected by thelaser radar to start a preceding vehicle determination process. After arequired determination time elapses, the detection of the precedingvehicle is determined.

An outline of a recognition process using the laser radar will bedescribed with reference to FIG. 18. In S1801, laser beams are emittedforward and reflected and returned laser beams are received. In S1802,relative distances are obtained from the time delay of the receivedlaser beams, and directions are obtained from the scan angles. In S1803,objects are grouped according to the relative distances after scanningis finished, to obtain a candidate object from which a predeterminednumber of beams or more are received. In S1804, based on the speed ofthe host vehicle and the relative speed, which corresponds to thedifference between the current relative distance to the candidate objectand the preceding relative distance thereto, a static object of whichthe relative speed is close to the speed of the host vehicle isexcluded. It is checked whether the candidate object continuously existsfor several hundreds of milliseconds. In S1805, the relative distance tothe object, the relative speed thereto, and the number of beams receivedfrom the object are output.

FIG. 5 illustrates a case where the host vehicle passes through thevicinity of the bottom of a gradient and suddenly finds a precedingvehicle. As in the case where the host vehicle passes through thevicinity of the top of a gradient, the sensor of the host vehicledetermines the presence of the preceding vehicle when the host vehiclecomes rather close to the preceding vehicle.

FIG. 6 illustrates a case where the host vehicle passes through thevicinity of a curve and suddenly finds a preceding vehicle. If thepreceding vehicle is suddenly recognized beyond the curve, the sensorrequires time to determine the presence of the preceding vehicle also inthis case.

FIGS. 16A to 16E illustrate an example of detection in a right-handcurve using the laser radar. When a preceding vehicle is found in theright-hand curve, the preceding vehicle is sequentially detected inorder of the right part on the rear of the preceding vehicle, the rightand center parts thereon, and the right, center, and left parts thereon.The preceding vehicle determination process is started when the threepoints at the right, center, and left parts on the rear of the precedingvehicle are detected. After the required determination time elapses, thepreceding vehicle is determined.

FIG. 7 illustrates a case where a preceding vehicle is suddenly foundbeyond an intersection. When the host vehicle changes its direction andfinds the preceding vehicle, the sensor requires time to determine thepresence of the preceding vehicle also in this case.

As described above with reference to FIGS. 4A to 4D and FIGS. 5 to 7, inorder to determine the preceding vehicle and to activate an actuator, itis necessary for the laser radar to detect the three points at theright, center, and left parts on the rear of the preceding vehicle andto monitor the detection state during the required determination time.

Next, a method of reducing the required determination time, according tothis embodiment will be described with reference to FIG. 8 andsubsequent drawings.

FIG. 8 is a process flow from sensor detection to vehicle control.

In S801, the sensor 201 detects obstacles and outputs data of anobstacle candidate. In S802, an obstacle determination process isperformed. In the obstacle determination process, the obstacle isdetermined based on duration in which the obstacle is being detected.Information of the obstacle, determined through the obstacledetermination process, is output. In S803, based on the host vehiclespeed and the distance and relative speed to the determined obstacle,the inter-vehicle control device 203 outputs control command values tocontrol the vehicle, such as a torque value, a brake oil pressure value,and a transmission command value. In S804, the inter-vehicle controldevice 203 activates an actuator to control the vehicle.

FIGS. 9A and 9B show timing charts of preceding vehicle detection. FIG.9A shows a conventional detection process. FIG. 9B shows a detectionprocess according to this embodiment.

In general, the sensor outputs information on a plurality of obstacles,and the inter-vehicle control section performs a preceding vehicledetermination process based on the sensor information, and performsactual vehicle control based on the determination result.

In a sensor output process, when an object satisfying a condition isdetected, the state of the detection process usually shifts from“detecting (1)” to “detecting (an object satisfying a condition isdetected) (2)” in which a result is output.

In a conventional determination process, the state of the detectionprocess shifts to “determining (3)” when information on the detectedobject is received from the sensor, and shifts to “preceding vehicledetermination (4)” after the object is continuously recognized for therequired determination time.

When the state of the detection process shifts to “preceding vehicledetermination (4)”, the inter-vehicle control section actuates theactuator.

A determination process of this embodiment is intended to reduce theduration of the state of “determining (3)”. As a result, information on“preceding vehicle determination (4)” can be rapidly sent to theinter-vehicle control section 209.

In the case of using the laser radar, as shown in FIG. 17A, when thethree points at the right, center, and left parts on the rear of thepreceding vehicle have been detected, the determination process isstarted, and the preceding vehicle is determined after the requireddetermination time elapses. With conventional techniques, the requireddetermination time is set to about three to five seconds.

In this embodiment, as shown in FIG. 17B, the required determinationtime can be reduced by using terrain information. For example, therequired determination time can be reduced to about 0.5 to 1 second.When the required determination time is reduced by about 2 seconds, thefree running distance is 36.1 meters if the host vehicle is driven at aspeed of 65 kilometers per hour, so that automatic deceleration can bestarted 36.1 meters short of the location where automatic decelerationis conventionally started. A time reduction in seconds is very importantfor vehicles driven at high speeds.

The course of a curve can be judged from a steering angle, a yaw rate,and map information of the position of the host vehicle. An obstacle maybe determined, for example, by reducing the number of points on theobstacle to be detected using laser beams, without waiting for theobstacle to come completely in front of the host vehicle. For example,in a curve, an obstacle may be determined through detection of twopoints on the obstacle, such as the left and center parts or the rightand center parts thereon.

Also in a case of using a stereo camera, the preceding vehicledetermination process can be similarly performed. The stereo cameraobtains the parallax between a right image and a left image to obtainthe distance to a corresponding point from the parallax. FIG. 19 showsthe principle of the stereo camera. The distance to an object and alateral location of the object can be measured.

FIG. 20 shows an outline of a recognition process using the stereocamera. In S2001, a stereo matching process is performed to obtainpoints where a right image matches a left image based on the right andleft grayscale images. In S2002, a range image calculation process isperformed to obtain the distance to each image point from the parallaxof the points. In S2003, a grouping process is performed according tothe distance. Through the grouping process, the size and the laterallocation of an object are recognized. In S2004, a selection process isperformed to exclude a static object based on the relative speeds ofgrouped objects, or to exclude an object outside an area specified by awhite road line if a white road line recognition function is provided.Further, an object which does not continuously exist for severalhundreds of milliseconds is excluded. In S2005, the relative distance,the relative speed, the lateral location, the width, and the height ofan object are output.

The object is continuously recognized and, when the requireddetermination time elapses, the object is determined to be a precedingvehicle.

Even if the object does not exist in front of the host vehicle, when itis recognized, by using information on a curve, that the object existsin the course of the curve for the required determination time, theobject may be determined to be a preceding vehicle. Further, when it isjudged that the host vehicle is traveling in a gradient, a criterion ofheight for an object is made smaller and, after the object is recognizedfor the required determination time, the object may be determined to bea preceding vehicle.

In this embodiment, the preceding vehicle determination time can bereduced by using terrain information.

Also in a case of using a millimeter wave radar, the preceding vehicledetermination process can be similarly performed. FIG. 21 shows anexample of a recognition process using the millimeter wave radar. InS2101, radio waves are emitted forward and reflected and returned radiowaves are received. In S2102, the distance to, the relative speed to,and the direction of a location from which a reflected radio wave havinga radio field intensity larger than a threshold is returned areobtained. It is possible to obtain the distance from the delay of areceived radio wave, the relative speed from the Doppler frequency, andthe direction from the scan angle.

In S2103, a static object of which the relative speed is close to thespeed of host vehicle is excluded. An object existing in another lane isexcluded from the obtained direction. An object that is recognized onlyfor less than about 300 milliseconds is excluded. In S2104, the relativedistance to, the relative speed to, and the direction of an object areoutput.

The object is continuously recognized, and, when the requireddetermination time elapses, the object is determined to be a precedingvehicle. Even if the object does not exist in front of the host vehicle,when it is recognized, by using information indicating that the vehicleis traveling in a curve, that the object exists in the curve for therequired determination time, the object can be determined to be apreceding vehicle.

In this embodiment, the required preceding vehicle determination timecan be reduced by using terrain information.

FIG. 22 collectively shows example determination conditions used forrespective sensors.

FIG. 10 shows data exchange between the obstacle determination processand the navigation device 202. Details of the obstacle determinationprocess will be described below. The obstacle determination processsends information on the following distance, to the navigation device202, and receives, from the navigation device 202, information on thegradients of the positions of the host vehicle and the preceding vehicleand information on the traveling directions of the host vehicle and thepreceding vehicle.

FIG. 11 shows a flowchart of the obstacle determination process. Detailsof a method of implementing the obstacle determination process will bedescribed. The obstacle determination process is usually called to beexecuted at intervals of 10 milliseconds, for example. In S1101, data isobtained from the sensor and checked. When a new obstacle is detected, apredetermined timer and a predetermined timer value are assigned. Whenan obstacle which was detected before is detected again, its timer valueis decremented. Further, when an obstacle has disappeared or has shiftedfrom the front of the host vehicle, the corresponding timer iseliminated. When there is an obstacle to be checked and a minimumrequired determination time (MIN) has elapsed, the judgment in S1102 isYes, the process flow advances to S1103 to make another judgment. Whenthe judgment in S1102 is No, the process flow returns. In S1103, it isjudged from the timer value whether there is an obstacle which existsover the required determination time. If the judgment in S1103 is Yes,the process flow advances to S1104 to determine the obstacle. If thejudgment in S1103 is No, the process flow advances to S1105 to perform aterrain condition search process (details thereof are shown in FIG. 12).After the terrain condition search process of S1105, the process flowadvances to S1106 to perform a terrain condition judgment process. If aterrain condition is established (Yes) in S1106, the process flowadvances to S1104 to perform the obstacle determination process. If theterrain condition is not established (No) in S1106, the process flowreturns.

In this embodiment, the terrain condition search process of S1105 andthe judgment process of S1106 are added, so that there is no need toalways wait for the required determination time to elapse and, when theterrain condition is established, the obstacle is determinedimmediately.

FIG. 12 is a flowchart of the terrain condition search process. InS1201, information on the following distance to the preceding vehicle issent to the navigation device 202 via the CAN. Next, in S1202,information on the gradients of the positions of the host vehicle andthe preceding vehicle and information on the traveling directions of thehost vehicle and the preceding vehicle are obtained from the navigationdevice 202. When the absolute value of the difference between thegradients is equal to or larger than a threshold or when the absolutevalue of the difference between the traveling directions is equal to orlarger than a threshold, the terrain condition is established (Yes) inthe judgment of S1203, and the process flow advances to S1204 to performa terrain condition flag setting process. When the terrain condition isnot established (No) in S1203, the process flow advances to S1205 toperform a terrain condition flag clear process.

FIGS. 13A and 13B illustrate how to obtain the gradient differences andthe traveling-direction differences. As shown in FIG. 13A, each gradientdifference is obtained from the difference between the gradients of thepositions of the host vehicle and the preceding vehicle.

FIG. 13B shows how to obtain the traveling-direction difference in acurve and in an intersection. The traveling direction of the hostvehicle is obtained from map information of the position of the hostvehicle or gyro information of the navigation device 202. The travelingdirection of the preceding vehicle is obtained from map information ofthe position of the preceding vehicle. Therefore, thetraveling-direction difference is obtained from the difference betweenthe traveling direction of the host vehicle and the traveling directionof the preceding vehicle.

Instead of the above-mentioned method, another method can be used inwhich the traveling direction difference is obtained from the radius ofcurvature of a curve and the following distance. A calculation method isshown in a formula 3.Traveling-direction difference=2×arcsin((Following distance/2)/Radius ofcurvature)  Formula 3

When the preceding vehicle exists beyond an intersection, thetraveling-direction difference can be obtained from the travelingdirection of the preceding vehicle and the traveling direction of thehost vehicle, obtained using a gyro or the like.

FIG. 14 shows a process performed in the navigation device 202. InS1401, information on the following distance is obtained via the CAN. InS1402, the gradients of and the traveling directions (travelingdirections of north, south, east, and west) at the positions of the hostvehicle and the preceding vehicle, which is the following distance aheadof the host vehicle, are obtained. In S1403, information on the obtainedgradients and traveling directions are sent via the CAN.

The obstacle determination process has been described in detail withreference to FIGS. 11 to 14.

As described above, the required determination time for an obstacle canbe reduced by using the terrain condition concerning a gradient or acurve obtained in the navigation device 202.

In the data exchange between the obstacle determination process and thenavigation device 202, shown in FIG. 10, the obstacle determinationprocess sends information on the following distance to the navigationdevice 202, obtains information on the gradients and the travelingdirections from the navigation device 202, and sets the terraincondition flags. However, in this embodiment, data exchange between theobstacle determination process and the navigation device 202 can beimplemented not only by the way shown in FIG. 10 but also by two exampleways to be described below.

First, an example of setting a terrain condition flag in the navigationdevice 202 will be described with reference to FIG. 23 and otherfigures.

FIG. 23 shows another data exchange (2) between the obstacledetermination process and the navigation device 202. The obstacledetermination process inquires a terrain condition of the navigationdevice 202, and obtains the terrain condition from the navigation device202. The navigation device 202 has an electronic map with terrainconditions.

An obstacle determination process is the same as that shown in FIG. 11,so a description thereof is omitted.

FIG. 24 shows another terrain condition search process (2). In S2401,the obstacle determination section 208 inquires a terrain condition ofthe navigation device 202 via the CAN. In S2402, a terrain conditionflag is received from the navigation device 202.

FIG. 25 shows another process (2) performed in the navigation device202. In S2501, an inquiry is received from the obstacle determinationsection 208 via the CAN. In S2502, based on the position of the hostvehicle, terrain information associated with the position of the hostvehicle is obtained from the map. In S2503, the setting of the terraincondition flag is sent to the obstacle determination section 208.

FIG. 26 shows a method of generating a map having terrain conditions. InS2601, information on the gradient and the traveling direction at eachlocation on a road map are specified such that the information can beretrieved. In S2602, the gradient difference and the traveling-directiondifference between a predetermined location (1) and a location (2) whichis a sensor-detection distance away from the predetermined location (1)are obtained. When one of or both of the gradient difference and thetraveling-direction difference are larger than respective thresholds,the terrain condition flag of the predetermined location (1) is set onin S2603. In S2604, the predetermined location (1) is associated withthe terrain condition flag on map data. In S2605, such map data isgenerated for the entire map by specifying locations at intervals offive meters, for example, to set the terrain condition flags there.

Since the locations are specified at intervals of the sensor-detectiondistance, changes in terrain tend to occur. Therefore, the requireddetermination time (MIN) may be set slightly longer.

In the data exchange (2) between the obstacle determination process andthe navigation device 202, shown in FIG. 23, a special map is used suchthat the terrain condition flag can be set in the navigation device 202.

Next, with reference to FIG. 27 and other figures, an example case wherethe obstacle determination section 208 obtains a terrain informationtable for traveling directions, from the navigation device 202 inadvance, and the terrain condition flags are set according toinformation of the terrain information table.

FIG. 27 shows still another data exchange (3) between the obstacledetermination process and the navigation device 202. The navigationdevice 202 sends the terrain information table to the obstacledetermination section 208 through still another process (3) performed inthe navigation device 202.

As shown in a lower part of FIG. 31, the terrain information tableincludes each distance, and the gradient and traveling direction at thelocation specified by the distance.

FIG. 28 shows still another obstacle determination process (3). Theobstacle determination process (3) of FIG. 28 is different from theobstacle determination process of FIG. 11 in that a terrain informationtable acquisition process in S2801 is added and still another terraincondition search process (3) in S2806 is used.

FIG. 29 shows the terrain information table acquisition process. InS2901, it is judged whether the terrain information table has beenreceived from the navigation device 202. When the judgment in S2901 isYes, the terrain information table is updated in S2902 and a post-updatedistance work for obtaining a running distance after the terraininformation table is updated is cleared in S2903. When the judgment inS2901 is No, the value of the post-update distance work is updated basedon the speed of the host vehicle and the calling interval of the terraininformation table acquisition process, in S2904.

FIG. 30 shows still another terrain condition search process (3). InS3001, it is judged whether the terrain information table has beenupdated. When the judgment in S3001 is Yes, the process flow advances toS3002. When the judgment in S3001 is No, which means that the terraininformation table has not been updated or is not used, so the terraincondition flag is cleared in S3006 and the process flow returns. InS3002, the terrain information table (the distance, the gradient, andthe traveling direction) and the post-update distance work are referredto.

In S3003, terrain information (the gradient and the traveling direction)of the location specified by a distance corresponding to the post-updatedistance is obtained. If the post-update distance falls within the rangeof two distances specified in the terrain information table, thegradient and the traveling direction are obtained through interpolationcalculation. In S3004, terrain information (the gradient and thetraveling direction) of the location specified by a distancecorresponding to “the post-update distance plus the following distance”is obtained. If the distance falls within the range of two distancesspecified in the terrain information table, the gradient and thetraveling direction are obtained through interpolation calculation.

In S3005, the gradient difference is obtained from the above-mentionedtwo gradients and the traveling-direction difference is obtained fromthe above-mentioned two traveling directions. When the absolute value ofthe gradient difference is equal to or larger than a threshold or whenthe absolute value of the traveling-direction difference is equal to orlarger than a threshold, the terrain condition flag is set.

FIG. 31 shows the process (3) performed in the navigation device 202. InS3101, the terrain information table for the traveling road (a travelingdistance from the current location, and the gradient and travelingdirection at the location specified by the traveling distance) isperiodically obtained. In S3102, the terrain information table is sentto the obstacle determination section 208 via the CAN.

With reference to FIG. 27 and other figures, the example case has beendescribed above, in which the obstacle determination section 208 obtainsthe terrain information table for the traveling directions, from thenavigation device 202 in advance, and the terrain condition flags areset according to information of the terrain information table.

The two example ways of data exchange between the obstacle determinationprocess and the navigation device 202 have been additionally describedabove.

Each of the determination conditions shown in FIG. 22 can be specifiedin the obstacle determination section 208 through the navigation device202 or another input means. Specifically, a minimum requireddetermination time, a required determination time, a detection methodused in a curve, and a detection method used in a gradient can bespecified.

ACC control is realized by the process of the inter-vehicle controlsection 209. In the ACC control, constant-speed control is performedwhen there is no preceding vehicle, and tracking control (feedbackcontrol of the following distance and the relative speed) is performedwhen there is a preceding vehicle. The inter-vehicle control section 209can perform pre-crash damage reduction control at the same time. Thepre-crash damage reduction control is used to perform brake control whena crash cannot be avoided and is activated when the time to collisionwith a preceding vehicle is 0.8 seconds or below.

Further, the inter-vehicle control section 209 can perform alarming,preliminary deceleration, and deceleration as shown in FIG. 32.Specifically, the inter-vehicle control section 209 can obtain the timeto collision (TTC) with the preceding vehicle, judges the value of theTTC, and perform the alarming, the preliminary deceleration, and thedeceleration. Further, the inter-vehicle control section 209 can changethe deceleration applied by the brake depending on the value of the TTC.

The TTC can be obtained by a formula 4 or by a formula 5 in whichacceleration is taken into account. The acceleration can be obtained bydifferentiating the hourly-measured host vehicle speed with respect tothe preceding vehicle speed (=host vehicle speed plus relative speed).TTC=relative distance to the preceding vehicle/relative speedthereto  Formula 4Relative distance+preceding vehicle speed×TTC+0.5×preceding vehicleacceleration×TTC×TTC=host vehicle speed×TTC+0.5×host vehicleacceleration×TTC×TTC  Formula 5

According to this embodiment, the obstacle determination time is reducedby the terrain condition, so that the activation operation of theinter-vehicle control section 209 can be performed earlier to avoid asudden recognition of a short following distance.

The first embodiment can be implemented as described above. In the firstembodiment, the effect can be recognized in driving at a gradient or ata curve. When a vehicle is driven in the same manner while a part of thefunction of the navigation device 202 is limited, for example, byblocking a GPS antenna, a difference in effect can be recognized andimplementation of the present invention can be checked.

FIG. 3 shows an obstacle recognition device according to a secondembodiment of the present invention, which includes the sensor 201 thatobtains the following distance and relative speed to a precedingvehicle, the navigation device 202 that obtains terrain information ofthe positions of the host vehicle and the preceding vehicle, and thecommunication cable 206 that connects the above-mentioned devices. TheCAN is used for communications performed between the above-mentioneddevices via the communication cable 206. The sensor 201 includes theobstacle detection section 207 that performs an input process in thesensor 201, and the obstacle determination section 208 that determinesrecognition of an obstacle. The sensor 201 sends an obstacle recognitionand determination result to the inter-vehicle control device 203 via theCAN.

Instead of the CAN, a dedicated communication cable may be used toexchange data between the navigation device 202 and the sensor 201.

Control processing according to this embodiment is realized by softwareprocessing, and the software is stored in the sensor 201 or thenavigation device 202.

FIG. 33 is another process flow (2) from sensor detection to vehiclecontrol. The process flow (2) of FIG. 33 is different from the processflow of FIG. 8 in that the obstacle determination process is implementedby the sensor 201 instead of the inter-vehicle control device 203.

The required determination time for an obstacle can be reduced by usingthe terrain condition concerning a gradient or a curve, obtained in thenavigation device 202, so that information about the obstacle can berapidly sent to the inter-vehicle control device 203. With the use of aninput section provided for the navigation device 202, the requireddetermination time can be set or changed due to terrain, byinstructions.

The obstacle recognition device can output, in addition to conventionalinformation about a number of obstacle candidates, determined-obstacleinformation obtained by using the terrain condition, which is a featureof this embodiment.

It is assumed that the obstacle recognition device can be implemented byusing a laser radar, a stereo camera, or a millimeter wave radar. Sincedetails of their processing are the same as those described in the firstembodiment, descriptions thereof are omitted.

In the obstacle recognition device, not only the laser radar, the stereocamera, and the millimeter wave radar but also any sensor which canobtain the relative distance and relative speed to a preceding vehiclecan be used. Further, it is also possible to use a sensor of which thedetection angle can be changed (vertically and horizontally) by usinginformation on the gradient of the position of the host vehicle andinformation on a steering angle, by a known technique.

The second embodiment can be implemented as described above.

What is claimed is:
 1. A vehicle control device, comprising: asensor-information input section that receives information from a sensorwhich detects an obstacle; a terrain-information input section thatreceives terrain information of the position of a host vehicle from amap database; an obstacle determination process section that determineswhether or not an obstacle is continuously detected until a given periodof time elapses after the sensor detects the obstacle, and thatdetermines that the obstacle is a preceding vehicle when the obstacle iscontinuously detected over the given period of time but that changesobstacle determination processing to determine that the obstacle is apreceding vehicle when the obstacle is not continuously detected overthe given period of time in order to perform a terrain search processbased on the terrain information of the position of the host vehiclereceived from the terrain-information input section, eliminate a need toalways wait for the given period of time to elapse, and shorten a timeto automatic deceleration.
 2. A vehicle control device according toclaim 1, wherein the terrain information of the position of the hostvehicle, received from the terrain-information input section, indicatesthat the host vehicle is located in a vicinity of a gradient road.
 3. Avehicle control device according to claim 1, wherein the terraininformation of the position of the host vehicle, received from theterrain-information input section, indicates that the host vehicle islocated in a vicinity of a curve.
 4. A vehicle control device accordingto claim 1, wherein the terrain information of the position of the hostvehicle, received from the terrain-information input section, indicatesthat the host vehicle is located in a vicinity of an intersection.
 5. Avehicle control device according to claim 1, further comprising afollowing distance control section that controls, based on a followingdistance to and a relative speed to the preceding vehicle determined bythe obstacle determination process section, the following distance tothe preceding vehicle.
 6. A vehicle control device according to claim 1,wherein the map database is implemented by a navigation device.
 7. Avehicle control method, comprising: receiving information at asensor-information input section from a sensor which detects anobstacle; receiving terrain information of the position of a hostvehicle at a terrain information input section from a map database; and,determining, at an obstacle determination process section, whether ornot an obstacle is continuously detected until a given period of timeelapses after the sensor detects the obstacle; determining, at theobstacle determination process section, that the obstacle is a precedingvehicle when the obstacle is continuously detected over the given periodof time; and changing, at the obstacle determination process section,obstacle determination processing when the obstacle is not continuouslydetected over the given period of time in order to perform a terrainsearch process based on the terrain information of the position of thehost vehicle received from the terrain-information input section,eliminate a need to always wait for the given period of time to elapse,and shorten a time to automatic deceleration.
 8. A vehicle controlmethod according to claim 7, wherein the received terrain information ofthe position of the host vehicle indicates that the host vehicle islocated in a vicinity of a gradient road.
 9. A vehicle control methodaccording to claim 7, wherein the received terrain information of theposition of the host vehicle indicates that the host vehicle is locatedin a vicinity of a curve.
 10. A vehicle control method according toclaim 7, wherein the received terrain information of the position of thehost vehicle indicates that the host vehicle is located in a vicinity ofan intersection.